1. Field of the Invention
The present invention relates to a battery module that includes a plurality of cells, and to an electricity storage device.
2. Description of Related Art
A battery module that is mounted as a power supply device to an electric automobile or the like is built as a combination of a large number of secondary cells, such as, for example, lithium ion battery cells, nickel-hydrogen battery cells, nickel-cadmium battery cells, or the like. Sometimes, with such a secondary cell, it may happen that the battery cell becomes damaged due to shock or vibration or the like, or that the internal pressure in the battery cell may rise and a gas including liquid in mist form containing electrolyte may leak out from the interior of the battery cell. Since there is a fear that this type of gas may ignite, it is necessary to vent it to the exterior of the battery module.
The following construction is per se known as such a gas discharge construction. A gas venting conduit is arranged above and in parallel with the plurality of battery cells and extends along the direction of arrangement of the battery cells, and through-holes are provided in this gas venting conduit correspondingly to the battery cells. A safety valve is provided to each of the battery cells, having a valve body made from rubber, a valve lid blocking this valve opening and communicating with the interior of the casing, and a tubular venting aperture above the valve lid, and having an conically shaped projecting portion at the upper external periphery of this venting aperture. And the valve opening of each of the battery cells is communicated with the gas venting conduit by the conically shaped projecting portion of this safety valve being fitted into an through-hole in the gas venting conduit (for example, refer to Japanese Laid-Open Patent Publication 2001-110377).